No, you won't get the same rush. IV'ing, as just noted by Euphoria, is always going to give you a stronger rush. Based on that information that Sam posted, that is just how you can figure out your dosage for various ROA. Hydromorphone has absolutely no rush when snorted, for me anyways. That is why I said that every single person I know who has done dilly's has always said to bang them. Some people I know even like the rush off IV'ed dilly better then IV herion.
It would equal to the same amount of Hydromorphone in your system, but it still wouldn't give the same effect, because IV'ing is obviously always going to be more intense. You will, technically, have the same amount in you, yes. If it takes you 8mg to get a nice feeling, then it would take you 2mg IV'ed to equal the same amount in your system, but the feeling won't be the same obviously, it just means that you get more bang for your buck when you IV, because it's 100% bioavailablity.
I fuckin love opes so much that I frequently get hard after snorting a line. I don't know why, probably because of the fact that you're opiating your brain and it makes you feel good and rewarded. Don't ask me how that gives you a hard-on, I don't really have any idea.